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V     V  \     . 

II  B  RAFLY 

OF  THE 
UN  IVERSITY 
Of    ILLINOIS 


550.5 
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cop.  2 
REMO"T 


STORAGE: 


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C3   5 


Field  Columbian  Museum 

Publication  44. 

Geological  Series.  Vol.  I,  No.  7. 


NEW  MINERAL  OCCURRENCES. 

11. 

CRYSTAL  FORMS  OF  CALCITE 
FROM  JOPLIN,  MISSOURI. 


BY 


Oliver  Cummings  Farrington,  Ph.D., 
Curator,  Department  of  Geology. 


Chicago,  U.  S.  A. 
February,  1900. 


221 
221 
224 


TABLE  OF  CONTENTS. 

New  Mineral  Occurrences,  ----- 

Inesite,     ----..'.. 

Caledonite,  ------- 

Gay-lussite,                                                          .            .                         .  226 

Kpsomite,     -            -            -                        .....  22g 

Golden  Calcite,              ---....  22Q 

Dolomite  Used  as  Indian  Money,             .....  2\o 

Crystal  Forms  of  Calcite  from  Joplin,  Mo.,        -          -          -  232 

Localities  of  Large  Crystals,         -           -           .                       .  .      232 

Forms  of  Large  Crystals,         ......  233 

Forms  of  Smaller  Crystals,           '           *           *           •           -  •      237 

Forms  of  Twinned  Crystals,    ......  238 


NEW  MINERAL  OCCURRENCES. 

1NESITE. 

SAN  CAYETANO  MINE  NEAR   VILLA  CORONA,   STATE  OF  DURANGO.    MEXICO. 

MUSEUM  No.  M  5> 

A  specimen  of  inesite  from  the  above  locality  was  first  secured 
by  the  writer  in  the  spring  of  1896  while  at  Villa  Corona.  Having 
later  determined  the  mineral  by  its  blowpipe  characters  as  inesite, 
a  request  was  sent  to  Mr.  John  D.  Almy,  one  of  the  proprietors  of 
the  mine,  to  procure  more  specimens  if  possible.  Through  his 
kindness,  and  that  of  Mr.  W.  H.  Schlemm,  a  few  more  specimens 
were  obtained,  and  were  generously  placed  at  the  writer's  disposal 
for  study.  The  rarity  of  the  mineral  makes  the  find  of  interest,  as 
it  is  known  at  only  three  other  localities  in  the  world,  viz. :  The 
manganese  mines  at  Nanzenbach,  northeast  of  Dillenburg,  Ger- 
many; the  Harstig  mine,  Pajsberg,  Wermland,  Sweden,*  and 
Jakobsberg,  Nordmark,  Sweden. t  In  the  specimens  from  the  San 
Cayetano  mine  the  mineral  occurs  partly  in  cavities  and  partly  in- 
tergrown  with  calcite  and  a  flesh-colored  manganesian  calcite. 
These  fill  narrow  veins  in  what  is  probably  an  altered  andesite. 
The  inesite  occurs  in  tufts  of  radiating  crystals  which  are  of  the 
characteristic  flesh-red  color.  The  most  characteristic  pyrognostic 
reaction  of  the  mineral,  noted  by  the  writer,  is,  that  when  heated 
in  the  closed  tube  it  becomes  opaque,  gives  off  water,  and  falls 
to  powder.  The  crystals  are  of  slender,  prismatic  habit,  averaging 
about  5  mm.  in  length.  None  were  found  doubly  terminated,  the 
attachment  at  one  end  preventing  the  development  of  faces  there. 
A  total  of  seven  forms  was  identified,  as  follows: 

a  (100),   b  (010),  c  (001),  g  (2oi), ' d  (on), 

k  (n. 0.12),  and  s  (946). 

Of  these  the    forms  k   (n. 0.12)    and    s  (946)    are    new.     The  form/* 
occurred  on  several  crystals,  the  form  s  was  found  on  but  one.      The 

♦Dana's  Mineralogy.  Sixth  Edition,  p.  564. 
••■First  Appendix  to  Dana's  Mineralogy.  1899. 

221 


222 


Field  Columbian   Museum — -Geology,  Vol.  i. 


table  following  gives  the  measurements  by  which  these  forms  were 
identified,  together  with  measurements  of  the  other  forms  noted. 
The  calculated  values  given  with  them  are  deduced  from  Scheieb's 
ratios  as  quoted  by  Dana.* 


No.  of 
Measurements. 


Limits. 


c  :  s=ool :  946  .... 

g:  $=201:946 

a:  s— 100: 946 

d :  $=011:946 

b'  :s—oio:  946 

c :  £=001:  Tf.0.12. 
A :  a' =11.0.12:  100. 
a  :  g=ioo  :20i . . . 
g  :  £=201  :ooi  . . . 
b' :d=olo  :  oil.  . . 

d:c=oil  :  001 

c  :  b=ooi  :  010. .  . 
a:  b=ioo  :oio  . . . 
b.a'=oio  :  Too. . . . 


79°  48' — 80°  42' 
520  36'—  550  34' 

11°  47'  — 12°  27' 

34°  36'—  35°  9' 
480  27' — 500  40' 
46°  25'—  46°  30' 
820  48"-84°  35' 
8o°  -86°  33' 
970  25' — 100° 


Observed. 
34° 

13°  23' 
19°  47' 
45°  20' 
84°  30' 
8o°  26' 
52°  25' 

12° 

34°  36' 
48°  34' 
46°  30' 
820  50' 

820  30' 

97°  25' 


The  crystal  faces  were  found  in  general 
to  be  fairly  flat  and  bright,  except  the  clino- 
pinacoids,  which  were  always  vertically  stri- 
ated, so  that  no  very  satisfactory  measure- 
ments could  be  made  from  them.  The  usual 
habit  and  development  of  the  crystals  is  illus- 
trated in  Fig.  1.  Fig.  2  shows  a  completed 
crystal  giving  the  new  forms,  k  (11. 0.12)  and 
s  (946)  in  their  relative  development. 


Calculated. 
34°  10' 

13°  30' 
190  48' 
45°  21' 
84°  33' 
8o°    9' 

53°    9#' 

120    5' 

34°  36K' 
49°  23' 
47°  22' 
83°  15' 
82°  35' 
97°  25' 


a       c     / 
'/  ■  1 

\    9 

—1, 6 

a      1 


Fig.  1— Inesite. 


Fig.  2— Inesite. 


An  analysis  of  the  mineral  was  made  by  the  writer.  For  this 
purpose  about  two  grams  were  laboriously  separated  from  the  calcite 
in  which  it  was  largely  embedded.  Experiments  were  first  made 
upon  the  temperature  at  which  water  was  driven  off  in  order  to  deter- 
mine, if  possible,  the  nature  of  its  existence  in  the  mineral.  About  a 
gram  of  the  finely  powdered  mineral  was  heated  at  successively 
increasing     temperatures     until     practically    constant    weight    was 


♦Dana's  Mineralogy,  p.  s6s. 


Feb.  1900.      New  Mineral  Occurrences — Farrington.  223 

obtained  at  each.  The  following  are  the  percentages  of  loss  obtained: 
At  no0,  3.88%;  at  2400,  1.94%;  at  3100,  0.10%;  at  faint  redness, 
1.00%;  total,  6.92%.  Of  the  above  amount,  5.99%  was  taken  up 
again  by  the  mineral  on  exposure  to  ordinary  air.  This  amount  may, 
therefore,  be  regarded  as  water  of  crystallization.  On  continuous 
heating  at  faint  redness,  the  mineral  turned  dark  and  showed  a  gain 
in  weight  doubtless  from  oxidation  of  manganous  compounds.  It 
was  evident,  therefore,  that  water  could  not  be  correctly  determined 
by  loss  upon  ignition. 

A  direct  determination  was  made,  therefore,  upon  a  separate 
portion  by  Penfield's  method,*  a  blast  lamp  being  used  for  the  final 
heating.  This  determination  gave  8.20%  of  water.  It  could  be  dis- 
tinctly seen  on  application  of  the  higher  heat  of  the  blast  lamp  that 
more  water  was  given  off  at  the  high  temperature,  showing  beyond 
question  that  some  of  the  water  was  present  as  water  of  constitution. 
If  the  percentage  of  water  taken  upon  exposure  to  air,  5.99%,  be 
regarded  as  water  of  crystallization,  then  the  remainder,  2.21%,  may 
be  considered  to  denote  the  percentage  of  combined  water.  This 
agrees  well  likewise  with  Barwald's  observations,  he  having  found 
1.97%  of  water  given  off  above  3000.  It  is  evident  from  the  above 
experiments  also  that  determination  of  water  as  loss  upon  ignition 
would  certainly  give  too  low  a  result.  This  may  account  for  the  low 
percentage,  7.17%,  obtained  by  Flink. 

The  remainder  of  the  analysis  was  performed  by  the  methods 
commonly  employed  for  the  analysis  of  silicates.  A  sodium  carbon- 
ate fusion  was  made,  the  bases  separated  from  silica  by  solution  with 
hydrochloric  acid,  iron  precipitated  by  ammonia,  manganese  by  bro- 
mine and  calcium  by  ammonium  oxalate.  Results  of  the  analysis 
with  ratios  are  as  follows  : 

, — „r  ati0 _ — , 

SiO* 4489  748  748  1.64 

MnO 36.53  5i7l 

FeO 2.48  034!         699  1.53 

CaO 8.24  148] 

MgO tr. 

H,Ocryst 5-^9  336)  4$6  u 

H,Oconst 2.21  i2of 

100.34 
Sp.  Gr.  (det.  by  Thoulet's  solution)  —  2. 965. 

The  ratio  of  Si  02  :  R  O  :  H20  is  thus  nearly  1.5  :  1.5  :  1.  Consid- 
ering the  ratio  of  water  of  crystallization  to  water  of  constitution 
s  3  :  i,  and  of  Mn  :  Ca  =  4  :  1,   the  formula  can    be  expressed   as 

♦Amer.  Jour.  Sci.,  3rd  Ser.,  Vol.  48,  p.  30. 

« 


224  Field  Columbian  Museum — Geology,  Vol.  i. 

4  H20,  6  (Mn,  Ca)  O,  6  Si  02,  or  H2  (Mn,  Ca)6  Si6  019  +  3H2  O.  Cora- 
paring  the  percentages  called  for  by  the  formula,  with  the  writer's 
analysis  calculated  to  ioo%  (reckoning  Fe  O  as  Mn  O),  the  results  are 
as  follows  : 

Analysis  Calculated 
Theory.  to  ioo. 

6  Si  Os 42.91  44.76 

|(6MnO) 40.51  38.86 

J(6CaO) 8.00  8.21 

4H,0 8.58  8.17 

100.  100. 

Here  the  greatest  discrepancy  to  be  noted  is  in  the  percentage 
of  Si  02,  which  is  noticeably  higher  in  the  analysis  than  the  theory 
calls  for.  Mn  O  is  also  a  little  lower.  Yet  it  is  believed  that  this 
formula  better  agrees  in  general  with  analyses  of  the  mineral  and  bet- 
ter expresses  its  constitution  than  any  hitherto  proposed.  Flink's 
formula,  2  (Mn,  Ca)  Si  03  -f-  H2  O,  reckons  all  the  water  as  water  of 
crystallization,  which  is  clearly  incorrect.  Moreover,  the  percent- 
age of  Mn  O  called  for  by  his  formula,  41.4%,  is  larger  than  has 
ever  been  obtained.  Barwald's  formula,  R  (ROH)2  Si3  08  +  acl-> 
gives  percentages  nearly  like  that  proposed  by  the  writer,  but  the 
compound  represented  by  such  a  formula  would  less  resemble  other 
zeolites  in  manner. of  constitution  than  does  that  of  the  writer's 
formula.  Moreover,  one  would  expect  a  darker  color  if  the  molecule 
Mn  OH  were  present  in  the  mineral. 


CALEDON1TE. 


STEVENSON-BENNETT  MINE,  ORGAN  MTS.,    NEAR  LAS  CRUCES,  NEW  MEXICO. 

MUSEUM  No.    M  5486. 


A  single  specimen  of  this  mineral  was  picked  up  by  the  writer 
on  the  dump  of  the  Stevenson-Bennett  mine  in  the  spring  of  1896. 
It  is  the  only  specimen  ever  found  there,  so  far  as  I  am  aware.  It 
is  also  the  second  or  possibly  the  third  occurrence  of  the  mineral 
reported  in  America.  It  is  known  to  occur*  at  the  Cerro  Gordo 
mines  in  California,  and  has  been  reported  from  Mine  la  Motte, 
Missouri,  but  the  report  needs  confirmation.  In  the  specimen 
secured  by  the  writer  the  mineral  is  in  the   form  of  several  distinct 

♦Dana's  Mineralogy,  p.  925. 


Feb.  1900.      New  Mineral  Occurrences — Farrington.  225 

crystals  which  occur  on  a  piece  of  the  quartz  gangue  common  at 
the  mine.  With  the  caledonite  crystals  are  associated  crystallized 
cerrusite,  massive  galena,  linarite,  and  wulfenite.  One  of  the  crys- 
tals of  caledonite  is  of  good  size,  being  5  mm.  in  length  in  the 
direction  of  the  vertical  axis,  and  3  mm.  in  length  in  the  direction 
of  the  macrodiagonal  axis.  The  other  crystals  are  smaller.  All 
are  developed  prismatically  in  the  direction  of  the  brachydiagonal 
axis,  and  are  attached  by  its  extremity.  The  crystals  are  of  a  deep 
bluish-green  color  and  transparent.  They  are  penetrated  to  some 
extent  by  cerrusite,  which  shows  as  darker  spots  when  seen  under 
a  lens.  These  portions  also  turn  brown  when  fragments  of  the 
mineral  are  heated  in  the  closed  tube.  Other  pyrognostic  charac- 
ters of  the  mineral,  noted  by  the  writer,  which  may  be  added  to 
those  given  by  Dana,  are:  In  the  closed  tube  it  decrepitates,  becomes 
black  and  opaque,  and  gives  off  water.  Fuses  easily  B.  B.  with 
intumescence  to  a  black  globule. 

The  crystals  were  fairly  well  suited  for  goniometric  measure- 
ment, and  the  following  forms  were  found,  the  position  and  letter- 
ing being  that  given  by  Dana: 

b  (010)  x  (201)  s  (223) 

c  (001)  /  (012)  t  (221) 

m  (no)  e  (on) 

The  development  of  the  different  crystals  was  found  to  be  qifite 
constant,  the  prominent  forms  being  c,  b,  m  and  s.  The  most  per- 
fect crystal  was  considerably  striated  parallel  with  the  direction  of  the 
brachydomes,  also  in  the  direction  of  the  zone  of  the  pyramids  and 
prism.  Owing  to  these  striations  but  few  really  accurate  measure- 
ments could  be  obtained,  but  a  few  were  secured  which  are  of  inter- 
est as  supporting  the  correctness  of  the  ratios  obtained  by  Busz* 
from  a  study  of  the  caledonite  of  Leadhills.  The  following  are  the 
measurements  which  it  was  possible  to  make  with  accuracy,  and 
for  comparison  are  given  the  values  as  calculated  by  Busz: 

Measured.  Calculated. 

d:m  =  (oio):(iio) 47°  26'  470  2.5'  30' 

W.;;/"'=(lI0):(lI0) 85°  12'  85°     9' 

s:s'" =(223): (22$ 66°  35'  66°  30'  34* 

^/jr=(ooi):(2oi) 710  52'  71°  53' 

X  :x'=(20\)\  (201) 360  15'  360  14' 

The  crystals  were  carefully  studied  also  in  the  hope  that  some 
measurements  might  be  found  which  would  throw  some  light  on  the 

*Neues  Jahrbuch  fur  Min.  Geol.  u.  Pal.  iSqs,  Band  I,  />.  in. 


226  Field  Columbian  Museum — Geology,  Vol.  i. 

disputed  question  as  to  whether  the  mineral  crystallizes  in  the  ortho- 
rhombic  or  monoclinic  system.  Owing,  however,  to  the  incomplete- 
ness of  the  crystals  on  account  of  their  attachment,  or  to  the  stri- 
ations  on  the  faces,  only  one  reliable  set  of  measurements  bearing 
upon  this  point  could  be  obtained.  These  were  measurements  of  the 
zone  c:x:x'  :c'  =(ooi)  :  (201)  :  (201)  :  (001),  as  already  quoted.  Com- 
pleting this  zone  by  difference,  the  angles  are  : 

r.-.x  =  (ooi)  :  (201)  —  710  52'. 

x:x'  =(201)  :  (20i)  =  36°  15'. 

x:c'  —{t.6\)  :  (ooi)  =  7i°  53'. 

Thus  the  brachydiagonal  is  an  axis  of  binary  symmetry  and  the 
mineral  must  be  regarded  orthorhom- 
bic.      As  noted  by  Busz  also,  the  habit 
of  the  crystals  gives  the  impression  of 
orthorhombic  symmetry. 

The  usual  development  of  the 
crystals  is  shown  in  Fig.  3.  ThSt[ 
shown  in  the  direction  of  the  brachy- 
diagonal is  necessarily  estimated,  as! 
no  crystals  doubly  terminated  in  the 
direction  of  this  axis  were  found.  The 
general  resemblance  in  habit  to  that 

of  cerussite  from   Rezbanya*  figured  fig-  3— caiedonite. 

by  Schrauf  will  be  noted. 


GAY-LUSSITE. 


SWEETWATER    VALLEY    NEAR    INDEPENDENCE    ROCK,    WYOMING. 
MUSEUM   No.  E  9695. 


On  dissolving  in  water  the  native  carbonate  of  soda  found  in  the 
Sweetwater  Valley,  Wyoming,  a  residue  of  clay  and  minute  crystals 
is  left.  Some  of  the  latter  were  kindly  forwarded  to  the  writer  by 
Prof.  W.  C.  Knight  of  the  University  of  Wyoming,  who  was  the  first 
to  notice  the  crystals,  so  far  as  I  am  aware.  A  test  of  the  pyrognos- 
tic  and  crystallographic  characters  showed  the  crystals  to  be  undoubt- 
edly gay-lussite.  They  are  microscopic  in  size,  none  that  I  found 
being  as  large  as  the  head  of   an   ordinary  pin.      More  exactly,  none 

♦Dana's  Mineralogy,  p.  287. 


Feb.  1900.      New  Mineral  Occurrences — Farrington.  227 

exceed  one  millimeter  in  the  direction  of  greatest  length.  They  are 
colorless  and  transparent  and  remain  so  with  the  exception  of  a 
slight  deliquescence  on  exposure  to  air.  In  distilled  water,  however, 
they  turn  white  and  in  a  short  time  become  pulverulent  from  solution 
of  sodium  carbonate.  The  crystal  forms  are  well  developed  and  the 
faces  fairly  sharp  and  bright.  In  habit  the  crystals  are  somewhat 
different  from  any  heretofore  described  on  account  of  the  relative 
subordination  of  e  (on)  and  the  relative  greater  prominence  of  r  (112) 
and  c  (001). 

The  following  forms  were  found  : 

c  (001),  m  (no),  e  (on),  r  (112). 

They  were  identified  by  the  following  measurements  : 

No.  of 
Measurements.  Limits.  Observed.       Calculated. 

m:m'"=\\o:\io 5  110°  41  -m°  11  no°  59'  1110  10' 

r.-/«=ooi:  no 2  83°  25-  830  30'  830  30'  830  30' 

cr=\oo:  112 2  430  13-  430  20'  4^°  20  43°  20' 

<r./=OOl:01I 7  540  10-  540  52'  54°  45'  54°  45' 

e:e'  =01 1 : oil 5  108°  59-1090  23'  1090  23'  1090  30' 

r:r'=ii2:  112 2  69  °  34'  69°  34'  690  29' 

m.'tf=iio:oil 4  420  17- 420  25'  420  25'  420  21' 

e  :  /— on:Tl2 4  270  22-  27°  29'  270  25'  270  44' 

m  :  t~  1 10: 1 12 2  530  10-  530  22'  530  10  530  10' 

The  accompanying  figure  (Fig.  4)  shows  the  usual  development 
of  the  crystals.     This  development  was  quite  constant  for  all  that 


Fig.  4— Gay-lussite. 


Fig.  5— Gay-lussite. 


were  examined.  Fig.  5  shows  the  same  forms  in  horizontal  projec- 
tion on  the  plane  of  the  clinopinacoid.  Here  is  better  shown,  too,  the 
relative  greater  length  of  the  crystals  in  the  direction  of  the  clinodi- 
agonal  axis.  The  faces  of  the  prism  w  (no)  are  usually  duller  in 
lustre  than  the  others,  and  the  basal  plane  c  (001)  is  often  striated 
parallel  to  the  edge  c  r. 


228  Field  Columbian  Museum — Geology,  Vol.  i. 


EPSOMITE. 

NEAR   WILCOX   STATION,  65   MILES  NORTH   OF  LARAMIE,  WYOMING. 
MUSEUM   No.  M  6126. 


An  account  of  the  above  occurrence  of  epsomite  was  given  the 
writer  by  Prof.  W.  C.  Knight  of  the  University  of  Wyoming,  in  a 
recent  letter.  He  writes:  "A  deposit  of  epsomite,  which  is  of 
variable  depth,  covers  an  area  of  90  acres  near  Wilcox  Station, 
Albany  County,  Wyoming.  In  the  spring  the  area  is  covered  with 
water  to  the  depth  of  a  foot  or  more,  forming  a  small  lake,  but  on  the 
advent  of  summer  the  water  evaporates  rapidly  and  an  abundant 
deposit  of  beautifully  crystallized  epsomite  is  left." 

A  few  of  these  crystals  were  received  from  Prof.  Knight  at  the  same 
time  by  the  writer,  but  not  being  able  to  study  them  immediately, 
they  became,  through  deliquescence,  unfit  for  thorough  crystallographic 
investigation.  I  have  thought  it  desirable,  however,  to  publish  an 
account  of  the  occurrence  so  that  any  who  may  visit  the  locality  may 
improve  the  opportunity  to  secure  material  whose  forms  may  admit 
of  exact  determination.  The  crystals  received  by  the  writer  are  from 
8  to  15  mm.  in  length  and  are  of  elongated  prismatic  habit.  Many 
are  doubly  terminated  and  have  pyramidal  planes  which  plainly  show 
sphenoidal  symmetry.    The  habit  of  the  crystals  and  the  fundamental 


Fig.  6— Epsomite. 

forms    are    shown  by  Fig,   6.     The   determination    of    the    pyramid 
z  (in)  depends  on  a  measurement  secured  as  follows  : 

Measured.  Calculated. 

m. -z=  1 10:  in  —  50°  30'  50°  55' 

While  some  of  the  crystals  have  only  the  simple  development 
represented  in  the  figure,  others  are  evidently  more  highly  modified, 
but  owing  to  the  deliquescence  previously  referred  to,  it  was  found 
impossible  to  determine  the  forms. 


Feb.  1900.      New  Mineral  Occurrences — Farrington. 


229 


GOLDEN  CALCITE. 


BAD  LANDS,  SOUTH  DAKOTA.     MUSEUM  No.  M  5904. 


On  breaking  open  the  concretions  found  in  beds  of  Fort  Pierre 
shale  in  the  region  of  the  Bad  Lands,  South  Dakota,  the  internal 
cavities  are  often  found  to  be  studded  with  crystals  of  calcite  of  a 
more  or  less  golden  yellow  color.  While  this  occurrence  of  calcite 
has  been  known  for  some  time,  the  form  of  the  crystals  has  not 
heretofore  received  description.  A  large  quantity  of  the  crystals 
having  been  collected  by  the  Museum  Expedition  to  the  Bad  Lands 
of  1898,  I  have  examined  them  with  the  following  results:  In  form 
the  crystals  are  all  simple  rhombohedrons  having  the  symbol  /,-2R. 
This  symbol  is  sufficiently  established  by  the  relation  of  the  cleav- 
age rhombohedron  to  the  crystal  form  and  by  several  measurements 
ranging  from  1010  25'  to  1010  35'  for/ :/=o22i  a  2021.  The  cal- 
culated value  is  1010  9'.  No  planes  could  be  found  which  were 
suited  to  accurate  measurement,  even  the  most  favorable  giving  only 
dim  and  elongated  reflections.  The  most  interesting  feature  of  the 
crystal  form  is  the  distortion  which  it  exhibits.  Although  some  of 
the  crystals  show  a  normal  development  of  the  rhombohedron,  the 
greater  number  are  lengthened  out  along  an  axis  normal  to  one  of 
the  rhombohedral  planes.  The  appearance  is  therefore  that  of  a 
monoclinic  crystal  made  up  of  a  prism  and  basal  planes.  This 
apparent  prismatic  form  is  made  more  striking  from  the  fact  that 
the  crystal  usually  rises  more  or  less  perpendicularly  from  its  plane 
of  attachment.  The  apparent  basal  plane  is  usually  more  or  less 
curved,  and  has  a  somewhat 
pearly  lustre.  The  prismatic 
planes  are  often  curved  as  well. 
The  length  of  the  apparent 
prisms  varies  from  a  few  milli- 
meters to  about  2  centimeters. 
The  form  of  these  crystals  is 
represented  in  Fig.  7.  Another 
form  of  distortion  is  shown  in 
Fig.  8.  Here  the  lengthening 
out  has  taken  place  in  two  direc- 
tions, so  that  an  apparently  flattened  rhombohedron 
results.      The  planes  of  such  crystals  show  a  curving 


Fig.  8-Golden  Calcite. 


Fig.  7— Golden 


7— Gold 
Calcite. 


230  Field  Columbian  Museum — Geology,  Vol.  i. 

similar  to  those  previously  described.  The  color  of  the  crystals  of 
all  types  varies  from  a  pale  yellow  to  a  deep  orange.  Some  are  per- 
fectly transparent,  but  the  majority  are  translucent  to  opaque.  The 
yellow  color  is  probably  due  to  the  presence  of  iron,  as  on  heating 
the  crystals  turn  black  and  become  slightly  magnetic.  Other  quali- 
tative tests  likewise  indicate  the  presence  of  considerable  iron. 


DOLOMITE  USED  AS  INDIAN  MONEY. 


NEAR  LAKEPORT,  LAKE  COUNTY,  CALIFORNIA.     MUSEUM  No.  M6387. 


Specimens  of  dolomite  from  the  above  locality,  and  of  the 
"  money  "  made  from  it,  were  collected  by  Dr.  G.  A.  Dorsey,  Curator 
of  Anthropology  of  the  Museum,  during  a  visit  made  in  1889  to  the 
Porno  Indians,  a  tribe  of  the  Kulanapan  stock  who  inhabit  the  region. 
The  material  has  long  been  used  as  a  medium  of  exchange  among 
these  Indians,  but  I  cannot  learn  that  it  has  been  hitherto  described. 

The  mineral  occurs  in  the  form  of  nodules,  or  boulders,  roughly 
oval  in  shape,  and  from  four  to  eight  inches  in  diameter.  They  are  of 
■  a  rusty  yellow  color  upon  the  surface  and  the  local  Indian  name  for 
them,  Pol'  -ka-be,  means  rusty  color.  A  freshly  fractured  surface 
shows  a  pure  white  color,  except  for  occasional  rusty  seams,  and 
lustre  like  that  of  unglazed  porcelain.  The  texture  is  compact  an,d 
fracture  flat  conchoidal.  A  determination  of  the  specific  gravity  of  a 
pure  white  fragment  gave  G.  =  2.878.  Dr.  Dorsey  did  not  visit  the 
mine  whence  the  dolomite  is  obtained,  but  was  informed  that  it  was 
situated  on  the  east  shore  of  Clear  Lake,  a  few  miles  southeast  of 
Lakeport. 

While  the  mode  of  occurrence  cannot  be  stated  with  certainty, 
it  is  probable  that  it  is  as  residual  boulders  in  a  reddish  clay. 

A  partial  analysis  by  the  writer  gave  Ca  O,  28.27%,  Mg  O, 
22.46%,  and  Fe  O,  1.18%.  These  percentages  are  nearly  those  of 
a  typical  dolomite. 

The  use  of  the  mineral  by  the  Indians  as  a  medium  of  exchange 
is  a  long  established  custom,  and  the  value  at  which  they  esteem  a 
well  worked  piece  is  nearly  equal  to  its  weight  in  gold.  In  order  to 
make  the  money,  symmetrically  shaped  cylindrical  pieces  are  cut  out 
from  the  crude  boulders.  These  are  burned  and  the  burning  brings 
out   reddish  streaks   of  color  doubtless  from  oxidation  of  the  iron, 


Feb.  1900.      New  Mineral  Occurrences — Farrington. 


231 


which  adds  to  the  beauty  of  the  pieces  in  the  eye  of  the  Indian.  The 
pieces  are  then  polished  and  perforated  and  pass  as  money,  the  local 
Indian  name  for  them  being  Po.  Many  of  the  small  pieces  are  also 
used  as  beads  for  necklaces  and  other  ornaments.  Fig.  9  shows  the 
appearance  of  two  typical  pieces  of  Po. 


Fig.  9. 


CRYSTAL  FORMS  OF  CALCITE  FROM  JOPLIN, 

MISSOURI. 


Large  crystals  of  calcite  from  Joplin,  Missouri,  have  been  known 
for  some  years  to  collectors,  and  have  become  widely  distributed  in 
collections.  The  crystals  are  remarkable,  not  only  for  their  size, 
but  for  their  transparency,  varied  color  and  the  perfection  of  their 
crystal  form.  So  far  as  I  can  learn  no  crystallographic  study  of 
these  calcites  has  ever  been  published.  Photographs  of  some  of 
the  crystals,  together  with  some  general  statements  as  to  the  occur- 
rence of  calcite  in  Missouri,  are  to  be  found  on  pp.  457-9  of  Vol. 
VII,  of  the  Reports  of  the  Missouri  Geological  Survey.  There  is 
also  mention,  on  p.  567  of  the  same  volume,  of  calcite  crystals  of 
large  size  occurring  in  Crystal  Cave,  Joplin,  and  some  description 
of  the  cave  is  given.  No  crystallographic  details  are  given  in  this 
account,  however,  the  crystals  being  simply  described  as  scaleno- 
hedral  or  rhombohedral.  The  present  study  of  some  of  the  crystal 
forms  can  in  no  sense  be  considered  a  complete  one,  since  the  only 
material  undertaken  to  be  described  is  that  comprised  in  the  Mu- 
seum collections,  and  some  crystals  that  were  kindly  loaned  for 
examination,  through  Prof.  J.  P.  Iddings,  by  the  University  of  Chi- 
cago. Having,  however,  cursorily  examined  a  large  number  of 
crystals  from  this  locality  as  exhibited  in  collections,  both  in  this 
country  and  in  Europe,  I  may  say  that  I  have  found  them  to  be 
remarkably  uniform  in  character,  and  hence  believe  the  character- 
istic forms  to  be  largely  comprised  in  the  types  here  described. 
The  specimens  in  the  Museum  collection  have  been  obtained  from 
various  sources,  chiefly  by  purchase  or  exchange,  but  some  were 
collected  at  the  mines  in  Joplin  during  the  spring  of  1898  by  Mr. 
H.  W.  Nichols,  Assistant  Curator  of  Geology. 

LOCALITIES  OF  LARGE  CRYSTALS. 

The  large  crystals  known  to  collectors  are  chiefly  of  two  types, 
differing  in  color  and  form.  Those  of  the  type  which  I  may  desig- 
nate as  Type  No.  1   are  characterized  by  a  delicate  violet  to  wine 

yellow  color,  often  showing  within  a  deeper  yellow  or  violet   light. 

232 


Feb.  1900.       Crystal  Forms  of  Calcite — Farrington.  233 

These  came  from  the  Blakie  No.  2  mine.  The  crystals  which  may 
be  designated  as  Type  No.  2  are  characterized  by  a  deep  amber 
yellow  color  ranging  to  colorless.  They  come  from  the  Crystal 
Cave,  Ino  mine.  These  two  mines  are  quite  near  one  another,  and 
are  both  located  in  Leadville  Hollow,  within  the  city  limits  of  Joplin. 

FORMS  OF  LARGE  CRYSTALS. 

Type  I . — Crystals  of  this  type  are  very  simple  in  form.  They 
are  made  up  of  the  common  scalenohedron  v,  -(-R3,*  truncated  by 
the  flatter  scalenohedron  /,  -\-}(K^.  The  average  development  of 
the  forms  is  illustrated  in  Fig.  1,  PI.  xxviii,  it  being  drawn  one-half 
size  from  one  of  the  crystals  in  the  Museum  collection.  Such  a 
size  is  usual  to  crystals  of  this  type.  The  following  are  averages 
of  measurements  of  several  angles  on  crystals  of  this  type,  as  made 
with  a  contact  goniometer: 

23i~4= 

3"i24= 

2131  = 

ion  = 

3~i2~i  = 

23U  = 

101*1  = 30 

The  surfaces  of  the  crystal  planes  on  these  crystals  are,  in  gen- 
eral, flat  and  bright  and  of  uniform  lustre.  They  are,  however,  more 
or  less  irregularly  marked  similar  to  the  planes  shown  in  Fig.  2, 
PI.  xxviii,  and  reentrant  angles  resulting  from  abortive  terminations 
often  occur.  While  the  crystals  are  often  doubly  terminated,  as 
illustrated  in  the  figure,  more  commonly  only  about  half  of  the  com- 
plete crystal  form  is  present,  the  plane  of  attachment  being  a  rhom- 
bohedral  or  a  basal  plane.  Numerous  planes  of  rhombohedral  cleav- 
age pass  through  the  crystals,  and  the  light  reflected  from  them  often 
brilliantly  illuminates  the  interior.  Many  crystals  are  also  often  iri- 
descent from  interference  colors  produced  by  parting  along  cleavage 
planes.  Irregularly  shaped  grains  of  marcasite  from  one  to  two  milli- 
meters in  diameter  often  occur  scattered  through  the  outer  layers  of 
the  crystals.  Other  associated  minerals,  often  well  crystallized  and 
found  more  or  less  in  contact,  are  galena,  dolomite  and  chalcopyrite. 
A  group  of  this  character,  now  in  the  Museum  collection,  is  shown  in 
the  frontispiece. 

*The  letters  used  are  Dana's. 


t:f 

=2134 

/./v 

=2134 

t:v 

=2134 

t :  cleavage 

=21*34 

v  :i/ 

=2131 

v  :  vv 

=2131 

v :  cleavage 

=2131 

sured. 

Calculated 

42° 

4i°  55' 

22° 

20°  36^' 

36° 

35°  56' 

160 

160  29' 

74° 

750  22' 

35° 

35°  36' 

3°° 

290    2' 

234  Field  Columbian  Museum — Geology,  Vol.  i. 

Type  2. — Crystals  of  this  type  are  characterized,  as  has  been  said, 
by  an  amber  yellow  color.  This  may  be  deeper  or  paler.  The  size 
of  the  crystals  is  also  remarkable.  Some  are  known  2^  feet  (.76 
meters)  in  length,  and  the  average  size  of  those  seen  in  collections  is 
from  6  inches  (.15  meters)  to  1  foot  (.30  meters)  in  length.  Those 
seen  in  collections  are  rarely,  if  ever,  doubly  terminated,  only  about 
half  of  the  complete  crystal  being  present.  Some  account  of  the 
mode  of  occurrence  of  these  crystals  in  a  cave  as  well  as  a  plan  of 
the  cave  is  given,  as  already  mentioned,  on  p.  567  of  Vol.  vii, 
Reports  of  the  Missouri  Geological  Survey.  For  the  following  fur- 
ther information  I  am  indebted  to  Mr.  Henry  Weyman,  the  present 
owner  of  the  cave  :  "  The  cave  is  from  250  to  300  feet  long,  from  40 
to  60  feet  wide  and  of  an  unknown  depth  in  places,  i.  e.,  we  have 
never  been  able  to  measure  the  bottom,  as  only  a  part  of  it  is  above 
water.  The  whole  opening  is  covered  with  crystals  of  various  sizes, 
leaving  no  place  on  any  of  the  roof  or  wall  exposed  and  going  down 
as  far  as  can  be  seen  in  the  water.  At  one  place  a  slab  covered  with 
large  crystals  has  fallen  from  the  roof  at  some  time,  and  since  then 
new  crystals  have  formed  on  the  roof  where  the  slab  has  been  broken 
away;  also  new  crystals  have  formed  on  the  broken  side  of  the  slab 
after  it  had  fallen  down.  The  largest  crystals,  I  should  think,  would 
measure  2  to  2^  feet  long.  The  greater  part  of  the  crystals  are 
doubly  terminated,  ending  in  very  sharp  points.  The  cave  was  dis- 
covered by  mining  after  lead  and  zinc  ore,  when  a  shot  put  in  the 
bottom  of  the  drift  broke  through  the  roof  of  the  cave  and  so  exposed 
the  mass  of  beautiful  crystals.  This  is  so  far  the  only  opening  allow- 
ing admittance  to  the  cave.  It  is  our  intention  to  preserve  the  cave 
in  its  present  state  and  make  access  to  it  more  convenient  to  visitors." 
It  is  also  stated  in  the  account  previously  mentioned*  that  the  cave 
is  remarkable  for  the  entire  absence  of  stalactites  of  the  usual  type. 
Since  these  are  absent  it  is  probable  that  the  cave  at  the  time  of  for- 
mation of  the  crystals  was  filled  with  water  holding  carbonate  of  lime 
in  solution,  from  which  crystallization  took  place.  Had  the  cave 
been  only  in  part  filled  with  water,  the  dripping  waters  would  doubt- 
less have  formed  stalactites  of  the  usual  type. 

The  form  of  the  crystals  of  Type  2  is  primarily  determined  by 
the  common  scalenohedron  v,  -\-  R3.  This  may  alone  constitute  the 
crystal  or  its  form  may  be  slightly  or  highly  modified.  A  common 
modification  is  the  truncation  of  the  apex  of  the  scalenohedron  by  the 
rhombohedron  <?,-^  R.      Fig.  2,  PL  xxviii,  represents  a  combination 


♦Report  of  the  Missouri  Survey  ioc.  cit. 


Explanation  of  Plate  XXVIII. 


Fig.  I.     Crystal  of  Type  I.  Fig.  2.     Crystal  of  Type  2. 
Joplin  Calcite.  Joplin  Calcite. 

One-half  natural  size.  One-half  natural  size. 

Mus.  No.  M5513.  Mus.  No.  M5621. 


FIELD   COLUMBIAN    MUSEUM. 


GEOLOGY,   PL.  XXVIII. 


FIG.     1 


Calcite,  Joplin,  Mo. 


LIBRARY 

UNIVERSITY  OF  ILLINOIS 

URBMA 


Feb.  1900.       Crystal  Forms  ok  Cai.cite — Farrington.  235 

of  these  forms  together  with  the  rhombohedron  /,  -  |  R,  as  seen  on  a 
crystal  in  the  Museum  collection.  There  is  also  present  one  plane 
of  the  negative  rhombohedron /,-2R. 

Some  measurements  made  on  this  crystal  with  the  contact  goni- 
ometer are  as  follows  : 

Measured.  Calculated. 

v.  I  -  2131    :   0445  =    43°-44'  44°    6' 

v  :/=  2131    :   0221   =    35°~38'  37°  41' 

e   :  /  =  01T2    :  0445  =   n°-i2°  120    2' 

e  xv  —  OlTa   :  2131   =    45°-52°  50°  36' 

As  has  often  been  observed  on  calcites  from  other  localities,  the 
planes  of  the  rhombohedron  c,-l/2  R  are,  in  this  crystal,  striated 
parallel  to  the  edge  r/r'.  They  are  also  somewhat  rounded.  The 
curious  sporadic  occurrence  of  the  plane  /  and  the  accompanying 
imperfect  growth  of  planes  seems  to  be  quite  common  for  Joplin 
crystals  showing  the  above  combinations.  At  least  the  writer  has 
noticed  the  same  appearance  on  several  other  similar  but  smaller 
crystals.  It  would  be  interesting  to  know  the  nature  of  the  molecular 
forces  which  would  uniformly  produce  degradation  of  this  sort.  The 
planes  of  the  scalenohedron  v  on  the  crystal  are  in  general  flat  and 
bright,  but  show  peculiar  markings  suggesting  stages  of  growth. 
These  markings  are  quite  irregular  in  form  and  seem  to  have  no 
angular  values  whatever.  They  follow,  however,  so  far  as  they  have 
any  arrangement,  the  lines  of  the  cleavage  rhombohedron.  Partings 
along  planes  of  this  rhombohedron  are  to  be  seen  through  the  crystal 
and  the  surface  of  attachment  is  usually  characterized  by  cleavage 
planes. 

Other  crystals  of  Type  2  are  more  highly  modified  than  the  one 
just  described.  Fig.  1,  PI.  xxix,  represents  one  such  crystal  now  in 
the  Museum  collection.  Here  the  primary  scalenohedron  v,  -J-  R3  is 
modified  by  the  scalenohedrons  n,  -f-  R£  and  w,  -J-  |  R2,  also  by 
the  positive  rhombohedronsr,  -(-  R  and  M,  -{-'4R,  and  by  the  negative 
rhombohedron /,-|R.  Only  about  half  the  complete  form  is  present 
in  the  specimen.  In  Fig.  2,  PI.  xxix,  is  shown  the  completed  ideal 
form  which  would  be  produced  by  these  combinations.  Some  of  the 
measurements  made  on  this  crystal  with  the  contact  goniometer  are 
as  follows : 

Measured.  Calculated. 

v    :   r    =2131  :  iofi  =  300  290  2' 

v    :  M   =  2131  :  4041  =  180  190  24' 

r  :  M    =  ioil  :  4041  =  310  310  \ox/l  ' 

v     :    l    =   2131  :  0445  =  44°  440  6' 


r 

:  / 

— 

IOII 

I 

:/' 

= 

0445 

V 

:  n 

— 

2131 

n 

:n' 

— 

4153 

n 

:  If 

— 

4153 

V 

:  w 

— 

2131 

w 

:iv' . 

= 

3145 

<w 

:  «A 

= 

3145 

236  Field  Columbian  Museum — Geology,  Vol.  i. 

Measured.       Calculated. 

0445=  40°  39°     4' 

4045  =  650  64°  S3JA  ' 

4153   =  !7°  14°  28^ ' 

45I~3  =  78°  78°     5' 

5^43  =  19°  180    7' 

3145  =  • 33°  33°  50' 

4l35  =  So"  49°  23 ' 

5~i43  =  l6°  l6° 

The  planes  of  r  are  further  identified  by  their  evident  parallelism 
to  the  cleavage  planes. 

An  interesting  peculiarity  of  the  specimen  is  the  surface  differ- 
entiation of  the  planes.  Thus  the  planes  of  the  scalenohedron  v  and 
the  negative  rhombohedron  /  are  flat  and  bright  ;  those  of  the  scalen- 
ohedrons  n  and  w  are  striated  parallel  to  the  adjoining  edges  of  the 
unit  rhombohedron,  and  the  planes  of  the  unit  rhombohedron  and 
the  rhombohedron  M  are  rough.  The  differentiation  closely  follows 
and  beautifully  illustrates  the  law  that  crystallographically  equivalent 
planes  are  similarly  affected.  An  examination  of  the  rough  planes 
reveals  but  little  in  the  way  of  symmetrical  etching  figures.  The 
roughness  is  caused  chiefly  by  delicate  pitting,  which  is  also  wholly 
irregular.  There  are  to  be  seen  occasional  pits,  however,  which  are 
larger  than  the  others  and  which  have  a  definite  pyramidal  shape. 
They  are  different  in  form  from  the  etching  figures  usually  produced 
artificially  on  calcite  by  hydrochloric  acid.  The  boundaries  of  the 
pits  lie  parallel  to  the  bounding  planes  of  the  unit  rhombohedron. 
Their  character  is  illustrated  in  the  accompanying  figure  (Fig.  10). 


Fig.  10— Growth  figures  on  plane  of  +R.    Calcite,  Joplin,  Mo. 


Explanation  of  Plate  XXIX. 


Fig.  i.     Crystal  of  Type  2. 
Joplin  Calcite. 
One-half  natural  size. 
Mus.  No.  M5515. 

Fig.  2.     Completed  ideal  form  of  crystal 
shown  in  Fig.  I. 


Fig.  3.    Crystal  of  Type  3. 
Joplin  Calcite. 
Mus.  No.  M5511. 

Fig.  4.     Crystal  of  Type  5. 
Joplin  Calcite. 
Mus.  No.  M5824. 


FIELD   COLUMBIAN    MUSEUM. 


GEOLOGY,   PL.    XXIX. 


FIG.   2 


FIG.    3 


FIG.    4 


Calcite,  Joplin,  Mo. 


LIBRARY 
UNIVERSITY  OF  ILLINOIS 

URBANA 


Feb.  1900.       Crystal  Forms  of  Calcite — Farrington.  237 

FORMS  OF  SMALLER  CRYSTALS. 

None  of  the  following  crystals  have  the  large  size  of  those  of  the 
types  above  described.  They  show,  however,  characteristic  combi- 
nations which  warrant  their  description  as  types. 

Type  3. — Crystals  of  this  type  are  illustrated  in  Fig.  3,  PI.  xxix. 
As  is  usual  with  the  Joplin  crystals  they  are  not  highly  modified, 
being  made  up  solely  of  the  scalenohedrons  v,  +  R3  and  w,  £  R2. 
The  specimens  of  these  crystals  in  the  Museum  collection  come 
from  the  Pelican  mine  in  Joplin,  occurring  with  sphalerite  on  the 
characteristic  chert  breccia  of  the  region.  A  large  group  is  shown 
in  the  frontispiece.  The  largest  single  crystal  is  not  over  4  inches 
(10  cm.)  in  length,  and  from  this  the  crystals  grade  to  a  very  small 
size.  Measurements  of  the  planes  made  with  the  reflecting  goniome- 
ter are  as  follows: 

Measured.  Calculated. 

V  :  v'    =2131:2311= 75°  25'  750  22' 

v :  v  ▼  =2131  :  3I21  = 350  36'  350  36' 

v:  v  vi=3~i2i  :  321!= 460  53'  470    \l/2' 

w.w'  =3145  :  3415= 50°  58'  49°  23' 

w.-a/v=3i45  :  4135= 150  59'  160 

The  most  striking  characteristic  of  these  crystals  is  the  fact,  repre- 
sented in  the  figure,  that  the  planes  of  scalenohedron  v  are  smooth 
and  brilliant,  while  those  of  w  are  rough.  This  differentiation  of 
planes  is  constant  for  all  the  crystals  which  have  come  under  the 
writer's  observation.  The  rough  planes  do  not  show  definite  etch- 
ing figures,  but  rather  under  a  lens  series  of  troughs  crossing  one 
another  and  following  the  lines  of  the  cleavage  rhombohedron.  In 
the  writer's  opinion  the  roughness  is  due  to  irregularities  of  growth 
of  the  crystals  rather  than  to  etching.  The  reasons  for  this  opinion 
are:  First,  it  is  difficult  to  conceive  of  any  etching  agent  which 
could  leave  the  planes  of  one  scalenohedron  so  entirely  untouched 
while  those  of  the  other  were  so  deeply  corroded.  Second,  on  sub- 
mitting the  crystal  to  the  action  of  weak  vinegar  as  an  etching  agent 
the  planes  of  the  scalenohedron  v  were  affected  much  more  rapidly 
and  noticeably  than  those  of  w.  The  etching  produced  by  the  vine- 
gar on  the  planes  of  V  was  in  the  forms  of  troughs  or  striae  follow- 
ing the  lines  of  cleavage,  on  7a  there  occurred  only  a  slight  additional 
roughening  of  the  planes.  It  is,  therefore,  in  the  writer's  opinion, 
not  always  correct  to  speak,  as  is  usually  done,  of  the  rough  planes 
as  etched  planes.  They  will  often  be  more  correctly  described  by 
the  term  imperfect  or  incomplete  planes. 


238  Field  Columbian  Museum — Geology,  Vol.  i. 

Type  4. — The  only  crystals  of  this  type  in  the  Museum  collec- 
tion come  from  Leddy's  Lease,  Central  City,  about  5  miles  from 
Joplin.  They  are,  however,  a  characteristic  type  for  the  Joplin  dis- 
trict. They  are  scalenohedral  in  character,  often  doubly  termi- 
nated, colorless,  and  frequently  reach  a  length  of  from  2  to  3  inches 
(5-7.5  cm.).  The  forms  characterizing  the  type  are  v,  +R3  domi- 
nant with  e,-}4K,  /,-2R  and  2,-nR,  subordinate.  A  characteristic 
feature  is  the  habitually  rounded  and  cross  striated  character  of  the 
planes  of  /.  In  fact  this  form  often  grades  into  a  scalenohedron  of 
large  indices,  the  symbols  of  which  it  is  impossible  to  determine. 
The  planes  of  /  likewise  usually  widen  toward  the  apices  of  the 
crystal,  so  as  to  crowd  out  the  planes  of  v,  and  themselves  define 
the  termination  of  the  crystal.  Fig.  1,  PL  xxx,  sufficiently  illustrates 
the  average  development  of  planes  on  crystals  of  this  type,  although 
the  one  figured  is  a  twin  crystal  and  larger  than  the  average  of  the 
type. 

Type  5. — Crystals  of  this  type  are  of  rhombohedral  development. 
Type  specimens  in  the  Museum  collection  come  from  the  Meadow- 
croft  mine,  Joplin.  They  are  colorless,  and  not  over  1  inch  (2.5  cm.), 
in  length.  They  are  made  up  of  the  negative  rhombohedrons  7/,-4R 
and/,-2R  dominant,  with  the  latter  truncated  by  e,  -J^R.  A  typical 
crystal  is  shown  in  Fig.  4,  PI.  xxix.  The  planes  of /and  rt  are  con- 
siderably curved,  and  admit  of  only  approximate  measurement.  The 
symbol  of/  was,  however,  sufficiently  determined  by  its  relation  to 
the  cleavage  rhombohedron,  and  that  of  rt  was  determined  from  the 
mean  of  measurements  of  ten  crystals,  which  gave  e  :  ^  —  0221  :  0441 
=  49°.  The  calculated  value  is  49°  32'.  The  planes  of  e  are  usually 
smooth  and  bright,  those  of/ are  deeply  striated  parallel  to  the  edge 
fy,  and  those  of  rt  parallel  to  the  longest  diagonal  of  the  rhomb. 
Rounding  of  the  planes  of  the  three  rhombohedrons  e,  /and  rt  into 
one  another  is  common.  One  crystal  showed  an  intermediate  rhombo- 
hedron between  e  and/  but  it  was  impossible  to  obtain  a  measure- 
ment sufficiently  satisfactory  to  determine  its  symbol.  In  some 
crystals  again  the  rhombohedron /is  absent  and  the  crystal  is  made 
up  of  only  the  forms  rh  -4R  and  e,  -^R. 

FORMS  OF  TWINNED  CRYSTALS. 

Only  a  few  twinned  crystals  were  noted  among  those  examined. 
The  larger  number  of  those  noted  are  twinned  upon  the  basal  plane. 
These  occur  of  both  Types  3  and  4.  The  crystal  chosen  for  special 
study  was  of  Type  4,  and  is  from  the  collection  of  the  University  of. 


Explanation  of  Plate  XXX. 


Fig.  i.     Basal  twin  of  Joplin  Calcite.       Fig.  2.     Ideal   form  of   twin   shown 
One-half  natural  size.  Fig.  I. 

University  of  Chicago  collection. 


FIELD   COLUMBIAN    MUSEUM. 


GEOLOGY,    PL.   XXX. 


FIG.    1 


FIG.    2 


Calcite,  Joplin,  Mo. 


LIBRARY 
UNIVERSITY  OF  ILLINOIS 

HQRfi N \ 


Feb.  1900.       Crystal  Forms  of  Calcite —  Farrington.  239 

Chicago.  The  crystal  is  shpwn  in  Fig.  1,  PI.  xxx.  Measurements 
made  in  the  zone  of  the  negative  rhombohedrons  on  this  crystal  with 
the  contact  goniometer  are  as  follows: 

Measured.  Calculated. 

^.■77=0112:0775        = 280  270  51' 

77.-/=o775  :o22i        = 9°  o°    I' 

e  :  /=OM2  :022I  = 360  36°  52 

e :  2"=oi  12  : 0.1 1. T i.i= 59K"  58°  29 

The  determination  of  JS"  rests  rather  on  its  occurrence  on  other  crys- 
tals of  this  type  which  could  be  measured  with  a  reflecting  goniome- 
ter, than  on  the  value  obtained  on  this  crystal,  it  being  presumed 
that  the  same  plane  was  most  likely  to  occur  again. 

The  peculiar  distortions  and  striations  exhibited  in  this  crystal 
are  illustrated  in  the  figure.  How  far  these  have  caused  it  to  depart 
from  the  normal  form  may  be  seen  by  comparing  Figs,  i  and  2,  PI. 
xxx.  The  tendency  shown  in  this  crystal  for  the  two  individuals  of 
the  twin  to  grow  by  one  another  and  partially  complete  themselves, 
is  quite  common  among  the  Joplin  twins.  Further  struggles  of  the 
molecular  forces  are  illustrated  by  the  number  of  abortive  planes  of 
e,  -^R,  these  being  so  numerous  as  to  produce  cross  striations  on 
/,  -2R.  The  latter  planes  are  further  rounded  from  the  tendency  to 
produce  scalenohedral  forms. 

Another  and  the  only  other  type  of  twin  crystal  noted  has  e, 
-J^R  as  the  twinning  plane.  Such  twins  occur  among  a  group  of 
calcite  crystals  formed  together  on  a  specimen  in  the  collection  of  the 
University  of  Chicago.  The  crystals  of  this  group  are  in  general 
scalenohedral  in  form,  colorless  to  amber  in  color,  and  vary  from 
1  to  2  inches  (.3  to  .6  cm.)  in  length.  Many  are  simple  crystals 
made  up  of  v,  +R3  dominant,  modified  by  e,  -^R,  /,  -2R,  and  a 
form  new  to  calcite,  fl,  -20R.  *  Others  are  intermediate  in  charac- 
ter, and  are  the  result,  doubtless,  of  one  individual  pushing  by 
the  other,  as  twins  on  the  base  have  already  been  shown  to  do.  Such 
a  crystal  is  represented  in  Fig.  1,  PI.  xxxi,  the  crystal  being  drawn 
in  the  position  of  the  negative  scalenohedron  in  order  better  to  show 
the  elongation  in  one  direction.  This  elongation  characterizes  the 
true  twins  as  well.      In  this  crystal  on  the   side  toward    the  observer, 

♦The  letter  given  to  this  form  was  chosen  in  accordance  with  Goldschmidt's  system,  Dr 
Charles  Palache  having  kindly  indicated  to  me  what  the  appropriate  letter,  according  to  this  sys- 
tem, would  bo.  I  do  not  feel  called  upon  to  apologue  forthus  combining  Oana'sand  Goldschmidt's 
lettering,  f  deem  it  essential  that  new  forms  should  be  lettered  in  accordance  with  Goldschmidt's 
system  in  order  to  avoid  conflict  of  letters,  but  the  common  forms  are,  and  are  long  likely  to  be, 
better  known  by  Dana's  letters. 


240  Field  Columbian  Museum — Geology,  Vol.  i. 

although  the  lower  part  of  the  crystal  is  quite  incomplete,  the  bound- 
ary planes  are  evidently  those  of  a  twin  crystal.  On  the  reverse  side, 
however,  the  development  is  that  of  a  simple  crystal. 

The  completely  formed  twins  resemble  in  many  respects  those 
from  Guanajuato,  described  by  Pirsson.*  The  twinning  plane  is  the 
same,  the  lengthening  out  in  one  direction  is  similar,  though  not  to 
the  extent  of  the  Guanajuato  crystals,  and  the  proportional  develop- 
ment of  the  faces  is  analogous.  The  Joplin  twins,  however,  differ 
notably  from  those  of  Guanajuato  in  their  development  at  the  apex  of 
the  salient  angle.  In  the  Guanajuato  twins  the  scalenohedral  planes  of 
the  two  individuals  of  the  twin  are  prolonged  at  the  apex  of  the  sali- 
ent angle  until  they  meet  in  a  point.  In  the  Joplin  twins,  however, 
the  scalenohedral  planes  of  each  individual  have  only  a  normal  devel- 
opment, and  there  is  no  prolongation  to  an  apex.  Some  crystals 
occur  in  which  one  individual  has  grown  by  the  other  at  the  salient 
angle  in  the  direction  of  the  vertical  axis  of  the  individual,  this  being 
but  another  illustration  of  the  curious  tendency  which  has  been  pre- 
viously noted.  There  is,  however,  no  prolongation  at  the  end  of  the 
twinning  plane.  The  Guanajuato  twins  are  usually  attached  at  the 
salient  angle,  while  the  reverse  is  true  of  the  Joplin  twins.  The 
attachment  of  the  Joplin  twins  by  the  reentrant  angle  often  takes 
place  at  the  end  of  a  projecting  process  of  calcite,  usually  more  or 
less  bounded  by  crystal  planes,  and  seeming  to  serve  as  a  sort  of  stem 
of  crystal  growth. 

As  regards  the  size  of  the  twin  crystals,  it  may  be  said  that  the 
longest  noted  measures  3  inches  (.75  cm.)  from  end  to  end  of  the 
vertical  axes.  The  lengthening  out  of  the  same  crystal  makes  it 
about  1  inch  (.25  cm.)  long  in  the  same  direction.  The  combination 
of  forms  which  make  up  these  crystals  has  already  been  indicated. 
The  determination  of  the  new  form  fl' ,  -  20R,  rests  upon  its  evident 
location  in  the  two  zones  v  v'  and  em  and  upon  a  very  accurate 
measurement  with  the  contact  goniometer  of  the  angle  e  :  12' = 
0221:0.20.20.1  =  24°.  The  calculated  value  is  23°  59'.  The  form 
usually  has  rounded  planes.  The  determination  of  the  other  forms 
likewise  rests  upon  measurements  made  with  the  contact  goniome- 
ter, but  these  correspond  so  closely  with  calculated  values,  and  the 
analogy  of  the  occurrence  of  the  forms  is  so  similar  to  that  of  the 
other  Joplin  calcites  that  there  can  be  little  doubt  of  their  being  cor- 
rectly identified.       The  form/2,  -£R,  is  quite  sporadic  in  its  occur- 


"Amer.  Jour.  Sci.  3d  Ser.,  Vol.  41,  p.  61. 


Explanation  of  Plate  XXXI. 


Fig.  i.     Partially  twinned  crystal  of        Fig.  2.     Twin  crystal  of  Joplin  Calcite. 
Joplin  Calcite.  Twinning  plane  e,-}£  R. 

University  of  Chicago  collection.  University  of  Chicago  collection. 

Fig.  3.  Same  crystal  as  Fig.  2,  drawn  in 
the  position  of  the  negative  scale- 
nohedron. 


■FIELD   COLUMBIAN    MUSEUM. 


GEOLOGY,   PL.  XXXI. 


FIG.    2 


FIG.    3 

Calcite,  Joplin,  Mo. 


LIBRARY 

UNIVERSITY  OF  ILLINOIS 

URSANA 


Feb.  igoo.       Crystal  Forms  of  Calcitk  -Farrington.  241 

rence,  appearing  sometimes  as  a  single  plane,  more  often  as  two,  and 
only  once  in  its  full  number  of  three  planes. 

In  conclusion,  the  following  list  includes  the  forms  noted  on  the 
Joplin  calcites  by  the  writer  : 

rtion,+£  n,  4153,  1 1  +R| 

J/,  4041, +i.ff  t/,2iji,  i8  +/?3 

w,  3145.  V 

'.on 2  -;./v'  /,2i34,  J«  +|7?2 

/.  0443  -I* 
^.0/75     I*  -f}A>3 

f,  0221   -2  A* 

9,0441     4  A' 
2?,  0.1 1.1 1.1,  -1 1  A' 
.Q,  1. 20.20. 1,  -20 A' 

It  is  evident  that  the  largest  variety  of  forms  occurs  in  the  zone 
of  negative  rhombohedrons.  Indeed,  it  is  hardly  likely  that  the 
above  list  includes  all  the  negative  rhombohedrons  which  occur,  as 
several  measurements  made  by  the  writer  indicated  others,  although 
they  could  not  positively  be  identified.  The  positive  rhombohedrons 
are  of  rare  occurrence  and  have  little  to  do  with  determining  the 
forms  of  the  crystals.  Among  the  scalenohedrons,  v,  +  R3,  is  almost 
universally  present  and  is  usually  the  dominating  form.  This 
scalenohedron  in  connection  with  e,  -|  R,  and/,  -2R,  determines  the 
habit  of  most  of  the  Joplin  crystals. 


UNIVERSITY  OF  ILLINOIS-URBAN* 


3  0112  061063910 


